Discrimination between poultry eggs on the basis of some observable quality is a well-known and long-used practice in the poultry industry. “Candling” is a common name for one such technique, a term which has its roots in the original practice of inspecting an egg using the light from a candle. As is known to those familiar with eggs, although egg shells appear opaque under most lighting conditions, they are in reality somewhat translucent and, when placed in front of direct light, the contents of an egg can be observed.
Eggs which are to be hatched to live poultry are typically candled during embryonic development to identify clear, rotted, and dead eggs (collectively referred to herein as “non-live eggs”). Non-live eggs are typically removed from incubation to increase available incubator space. In many instances it is desirable to introduce a substance, via in ovo injection, into a live egg prior to hatch. Injections of various substances into avian eggs are typically employed in the commercial poultry industry to decrease post-hatch mortality rates or increase the growth rates of the hatched bird. Examples of substances that have been used for, or proposed for, in ovo injection include vaccines, antibiotics and vitamins. Examples of in ovo treatment substances and methods of in ovo injection are described in U.S. Pat. No. 4,458,630 to Sharma et al. and U.S. Pat. No. 5,028,421 to Fredericksen et al.
In ovo injections of substances typically occur by piercing an egg shell to create a hole therethrough (e.g., using a punch or drill), extending an injection needle through the hole and into the interior of the egg (and in some cases into the avian embryo contained therein), and injecting one or more treatment substances through the needle. An example of an in ovo injection device is disclosed in U.S. Pat. No. 4,681,063 to Hebrank. This device positions an egg and an injection needle in a fixed relationship to each other, and is designed for high-speed automated injection of a plurality of eggs. The selection of both the site and time of injection treatment can impact the effectiveness of the injected substance, as well as the mortality rate of the injected eggs or treated embryos. See, for example, U.S. Pat. No. 4,458,630 to Sharma et al., U.S. Pat. No. 4,681,063 to Hebrank, and U.S. Pat. No. 5,158,038 to Sheeks et al.
In commercial poultry production, only about 60% to 90% of commercial broiler eggs hatch. Eggs that do not hatch include eggs that were not fertilized, as well as fertilized eggs that have died. Infertile eggs may comprise from about 5% up to about 25% of all eggs in a set. Due to the number of non-live eggs encountered in commercial poultry production, the increasing use of automated methods for in ovo injection, and the cost of treatment substances, an automated method for identifying live eggs and selectively injecting only live eggs, is desirable.
In commercial turkey production, a significant number of valuable eggs die during the hatching process. These deaths could be prevented by various intervention techniques such as cracking the air cell to aid pipping, placing the egg in a more oxygen rich environment, placing the egg in a warmer environment, and/or administering treatment (e.g., a thyroid releasing hormone). Unfortunately, it can be difficult to detect eggs that require intervention.
There are other applications where it is important to be able to identify live and non-live eggs. One of these applications is the cultivation and harvesting of vaccines in live eggs (referred to as “vaccine production eggs”). For example, human flu vaccine production is accomplished by injecting seed virus into a chicken egg at about day eleven of embryonic development (Day-11 egg), allowing the virus to grow for about two days, euthanizing the embryo, and then harvesting the amniotic fluid from the egg. Typically, eggs are candled before injection of a seed virus to facilitate removal of non-live eggs. Vaccine production eggs may be candled one or more days prior to injection of a seed virus therein. Identification of live eggs in vaccine production is important because it is desirable to prevent seed vaccine from being wasted in non-live eggs and to reduce costs associated with transporting and disposing of non-live eggs.
U.S. Pat. Nos. 4,955,728 and 4,914,672, both to Hebrank, describe a candling apparatus that uses infrared detectors and the infrared radiation emitted from an egg to distinguish live from infertile eggs. U.S. Pat. No. 4,671,652 to van Asselt et al. describes a candling apparatus in which a plurality of light sources and corresponding light detectors are mounted in an array, and wherein eggs are passed on a flat between the light sources and the light detectors.
Japanese Patent No. JP9127096A2 describes an apparatus that detects pulse rate of egg embryos in order to identify live and dead eggs. PCT Publication WO 02/086495 describes an apparatus for determining the viability of an egg by detecting heart rate. USSR Patent Application No. SU1226308A1 describes scanning egg embryos for the presence of blood vessels in order to determine viability. U.S. Pat. No. 3,540,824 describes a method and apparatus for detecting heart beats in incubating egg embryos. U.S. Pat. No. 6,488,156 describes the use of electrical sensors placed on the shell of an egg for the purpose of measuring heart rate.
As in humans, the heart rate of a bird, such as a chicken, can indicate the condition or health of the bird. In the extreme, absence of a heart rate can indicate death. With respect to humans, a heart rate in the range of 60 to 180 beats per minute can indicate metabolic load (i.e., the amount of oxygen that needs to be transported through the body), health, and/or the condition of the heart itself. The heart rate of a Day 18 chicken embryo is typically between about 200 and 300 beats per minute in an incubator at 37° C. Removing the egg from the incubator and into an area with a lower temperature, such as a room at 25° C., produces a characteristic heart rate pattern. First, heart rate accelerates by about 20%, presumably as the animal is awakened or startled by the motion, light, or perhaps even sound or vibration. After two or three minutes, the embryo heart rate settles back down and then slowly declines to about 50% of the baseline heart rate over forty-five minutes as the egg slowly cools, as illustrated in FIG. 1. Thus, although embryo heart rate can be used to indicate the health or condition of the embryo, its accuracy can be affected because of the effect external stimuli and environmental conditions surrounding an egg can have on the embryo.
In addition to heart rate detection methods, the detection of embryo motion can be indicative of a live egg. Detection of embryo motion and embryo heart rate can be performed by monitoring changes in light levels within an egg when the egg is illuminated with light from a candling apparatus. Embryo motion produces relatively large signals so that there are few false lives (i.e., non-live embryos indicated as live) created by external disturbances, vibrations, etc. imparted to an egg carrier. However, not every live embryo will move in a given time interval, so false deads (i.e., live embryos indicated as dead) can be common for candling intervals of ten seconds and less. Detection of an embryo heart rate may require, for example, about a hundred-fold increase in sensitivity as compared with embryo motion detection. However, an embryo heart rate provides a continuously available signal.
To reduce the number of false lives as a result of external disturbances, heart rate detection candling systems are generally configured to detect multiple cycles of an embryo heart rate. Unfortunately, longer candling times generally decrease egg throughput and typically require more candling detectors in order to compensate for the longer candling times. Heart rate detection methods that allow faster detection times with fewer false lives caused by external vibrations are desirable.